The present invention relates generally to dampers, and more particularly to a method for attaching a ring to a damper base cup and to a damper having a ring.
Conventional dampers include dampers, such as conventional vehicle shock absorbers, having a cylinder containing a damping fluid (such as oil) and having a damper piston assembly including a piston which slideably engages the cylinder. The fluid passes through an orifice of a valve assembly of the piston. A piston rod has a first end attached to the piston and a second end extending outside the cylinder. The cylinder and the rod are attached to separate structures to dampen relative motion of the two structures along the direction of piston travel. Typically, a base cup is attached to the cylinder, and a circular, continuous or split ring is resistance spot welded, without using filler material, to the convex surface of the base cup and/or is gas-metal arc welded, using filler material, with two side welds to the convex surface of the base cup. One of the two structures is attached to the cylinder through the ring.
Using only the resistance spot weld to attach the ring to the base cup results in high fatigue stress mainly due to the limited weld bond area, especially when side loads are involved. Using only the two gas-metal side arc welds creates the problem of having a filler-material weld bead laid on a large root gap leading to variable fatigue life. Also, if both side welds are made at the same time, their cooling stresses add up and solidification stresses are high. If the side welds are made one after another, the Takt time (i.e., the time from the start of making a first part to the start of making a second part) is high as the part needs to be fixtured while the first weld cools in order to minimize distortion of the cup-ring assembly. If both a resistance spot weld and the side welds are used, this adds to the cost and the Takt time of joining the base cup to the ring. When a continuous ring (such as a seamless ring) is used, it is more expensive then to use a split ring. When a conventional split ring (such as a less expensive split ring formed from sheet metal) is used, it looks like a continuous ring which has a cut, and it is difficult to reliably locate the cut at the weld area leading to a rejected part.
What is needed is an improved method for attaching a ring to a damper base cup and an improved damper having a ring.
A first method of the invention is for attaching a split ring to a base cup of a cylinder of a damper and includes steps a) through d). Step a) includes obtaining a generally-circular split ring having a center and having opposing first and second end portions, wherein the first end portion has a first tab which projects radially outward. Step b) includes positioning the split ring proximate the base cup. Step c) includes aligning the tab to project toward the base cup. Step d) includes autogenously welding the split ring to the base cup creating a weld bond area which includes at least a portion of the first tab and at least a part of the second end portion.
A second method of the invention is for attaching a continuous ring to a damper base cup and includes steps a) through d). Step a) includes obtaining a damper base cup having a substantially convex surface, wherein the substantially convex surface has a first outward projection. Step b) includes positioning the continuous ring proximate the base cup. Step c) includes aligning the first outward projection toward the continuous ring. Step d) includes autogenously welding the continuous ring to the base cup creating a weld bond area which includes at least a portion of the first outward projection.
A third method of the invention is for attaching a continuous ring to a damper base cup and includes steps a) and b). Step a) includes locating the continuous ring proximate the base cup. Step b) includes autogenously welding the continuous ring to the base cup.
In a first embodiment of the invention, a damper includes a damper cylinder, a base cup attached to the damper cylinder; and a generally-circular split ring. The split ring has a center and has opposing first and second end portions. The first end portion has a first tab which projects radially outward. The split ring is autogenously welded to the base cup creating a weld bond area which includes at least a portion of the first tab and at least a part of the second end portion.
In a first expression of a second embodiment of the invention, a damper includes a damper cylinder, a base cup attached to the damper cylinder, and a continuous ring. The base cup has a substantially convex surface, wherein the substantially convex surface has a first outward projection. The continuous ring is autogenously welded to the base cup creating a weld bond area which includes at least a portion of the first outward projection.
In a second expression of a second embodiment of the invention, a damper includes a damper cylinder, a base cup attached to the damper cylinder, and a continuous ring autogenously welded to the base cup.
Several benefits and advantages are derived from the invention. In the method and damper embodiment of the invention having the split ring with the projecting tab, an inexpensive split ring is used, the tab is easily located at the weld area, and only one weld operation is used wherein the tab creates a larger weld bond area providing improved fatigue life. In the method and damper embodiment and expression of the invention having the continuous ring and having the base cup with an outward projection, only one weld operation is used wherein the outward projection creates a larger weld bond area providing improved fatigue life. In the method and damper embodiment and expression of the invention having the continuous ring, with or without an outward projection, only one weld operation having a larger weld bond area is used which provides improved fatigue life.